It is generally known to utilize thermoplastic multilayer structures, such as films, sheets or the like, to package products. For example, typical products packaged with thermoplastic multilayer structures include perishable products, such as food. Specifically, meats and cheeses are typically packaged in thermoplastic structures. In addition, it is generally known that cook-in structures may be utilized to package food products, whereby the products are then heated to cook the food products contained within the packages. Moreover, shrink films are known for packaging food products, such as meat and cheese.
One type of meat that may be packaged within thermoplastic multilayer structures is bone-in meat. Bone-in meat products often contain sharp bones that protrude outwardly from the meat. Typical cuts of bone-in meat include a half carcass cut, hindquarter cut, round with shank, bone-in shank, full loin, bone-in ribs, forequarter, shoulder and/or other like cuts of meat. When bone-in meat products are packaged and/or shipped, the protruding bones often can puncture or tear the packaging materials. This puncturing or tearing of the packaging material by the protruding bones can occur at the initial stage of packaging or at the later stage of evacuation of the packaging, which may expose the bone-in meat products to oxygen and moisture, thereby having deleterious effects on the bone-in meat product.
Many techniques and products have been developed for preventing bone puncture or tear. U.S. Pat. No. 6,171,627 to Bert discloses a bag arrangement and packaging method for packaging bone-in meat using two bags to provide a double wall of film surrounding the cut of meat for bone puncture resistance.
U.S. Pat. No. 6,015,235 to Kraimer discloses a puncture resistant barrier pouch for the packaging of bone-in meat and other products.
U.S. Pat. No. 6,183,791 to Williams discloses an oriented heat-shrinkable, thermoplastic vacuum bag having a protective heat-shrinkable patch wherein the heat-shrinkable patch substantially covers all areas exposed to bone, thereby protecting the bag from puncture.
U.S. Pat. No. 5,020,922 to Schirmer discloses a seamless puncture resistant bag which includes a length of lay-flat seamless tubular film folded to a double lay-flat configuration. The configuration forms a seamless envelope with one face thickened integrally to triple thickness.
U.S. Pat. No. 5,534,276 to Ennis discloses an oriented heat-shrinkable, thermoplastic vacuum bag having a protective heat-shrinkable reverse printed patch attached to the bag.
The art teaches many techniques for addressing the problem of bone puncture or tear in the packaging of bone-in meat products. Many of the solutions typically include a film structure or bag having patches, double-walled thicknesses or the like. However, a need exists for multilayer structures that may be utilized for packaging bone-in meat products and other like products that have sufficient durability, strength, and puncture resistance so as to keep the multilayer structures from being punctured by bony protrusions from the meat, and yet is heat-sealable so as to form packaging that can seal to themselves or other structures. In addition, there exists a need in the art for economical and commercially viable multilayer structures to form heat-sealable and heat-shrinkable packages for bone-in meat products.
One solution for packaging bone-in meat entails the utilization of coextruded multilayer structures having sufficient strength, durability, tear resistance, puncture resistance, and optical properties. However, the formation of coextruded multilayer structures having these properties is difficult without laminating the structures to provide double-walled structures and/or laminating or otherwise adhering patches to the structures. Laminating structures together to form double-walled structures or otherwise adhering patches to the structures requires multiple complicated processes, thereby requiring additional time and money.
For example, known coextruded structures that may be useful for the present invention require very thick coextrusions to provide adequate puncture resistance for bone-in meat. This requires the use of large quantities of fairly expensive polymeric materials to provide the protection against puncture and tearing. This problem is typically solved, as noted above, by laminating structures together to form patches in the areas of the structures most susceptible to breaking or puncturing. These patches, while allowing the use of less thermoplastic material, can be unsightly in that the surface of the films are interrupted by the patches. In addition, the lamination process of adding the patches to the films can cause decreased optical characteristics, in that patches can become hazy or yellow. Moreover, the areas of the patches also suffer from decreased optical properties due to the thicknesses of the patches and the patches tend to interfere with the shrink characteristics of the structures. Still further, the application of the patches requires extra steps in addition to the steps of making the structures, including precisely positioning the patches where bony protrusions are likely to be.
In addition, many coextruded structures having the durability and strength to package bone-in meat have sealability problems. As noted above, the structures must be fairly thick to provide adequate puncture resistance. Typically, heat-sealing bars are utilized to seal the structures together. If a structure is too thick, the sealing bars will have difficulty in transferring an adequate amount of heat to the heat-sealing layers to melt the heat-sealing layers of the structures to provide adequate heat-seals. Inadequate heat-seals cause leaks, thereby exposing products contained within packages made from the structures to both oxygen and moisture, which may deleteriously affect the products.
In addition, thicker structures tend to have a decrease in optical properties compared to relatively thinner structures. A structure's thickness is directly related to haze. Thicker structures, therefore, tend to have an increase in haze, thereby contributing to a decrease in the clarity of the structures. In addition, thicker structures tend to be more difficult to orient. Thicker structures tend to have a lower shrink energy, thereby requiring an increase in orientation ratio to provide similar shrink characteristics as compared to thinner structures.
A need, therefore, exists for coextruded multilayer structures having superior strength, durability, tear resistance and puncture resistance that are significantly thinner than known structures while maintaining superior optical properties, such as low haze, low yellowness, and high clarity. In addition, a need exists for coextruded multilayer structures that are orientable to provide packages that are heat shrinkable around products. In addition, coextruded multilayer structures are needed having superior sealability as compared to known structures, while still maintaining the superior strength, durability, puncture resistance, tear resistance and optical properties. In addition, methods of making the multilayer structures and packages made therefrom are needed.